“Canon has a built-aperture mount adapter on a patent pending. Because the lens image circle can afford that extra light ghost in it may cause, Canon seems to have addressed by an internal aperture in the adapter. Canon’s next generation camera that sounds like little by little starting to move.
. Patent Publication No. 2011-107255
2009.11.13 filing date
. Conventional mount converter
Adjust the flange back only
Not consider the difference of the image circle, causing unwanted ghost light
. Canon patent
Aperture converter having an adjusting means
Aperture and manual operation of locks available
And electric drive aperture, the lens can be controlled by information
With a means of communication”
Egami, Google Translation from Japanese.